I am very grateful to my thesis supervisors, Dr. Dan Graur and Dr. Reed A. Cartwright, for their guidance, encouragement, patience, and support during the course of this work. I have encountered may difficulties, but your help made this thesis possible.

I would like to thank Dr. Yuriy Fofanov and Dr. Shishir Shah for being my thesis committee members and providing valuable suggestions.

I would like to thank my lab mates, Dr. Giddy Landan, Dr. Kiyoshi Izawa, Dr. Niv Sabath, Nicholas Price, Longyi Qi, and Yichen Zheng. I had a great time in this lab for two years and learned a lot.

I would like to thank my other friends in the University of Houston for all their support, entertainment, and caring.

My special thank goes to my wife Bingjun Zhang, my parents Dr. Wenyuan Zhao and Yijun Wang, and my previous supervisor when I was in China, Dr. Kui Lin. They are the most important persons in my life. To them I dedicate this thesis.
